An elevation is different. It shows the face of something, or perhaps more correct, the projection of an object/s to a plane. But my testing suggests it produces SECTIONS, not elevations.
Yes, you can use abbreviations in tables and figures. All abbreviations used in tables and figures should be defined in the table note or figure caption, respectively, even though the abbreviations will be also be defined in the text if they are used there.
When an abbreviation can be used to refer to a singular thing  a run batted in, a meal ready-to-eat, a prisoner of war  it's surely a good idea to form the plural by adding s to the abbreviation: RBIs, MREs, POWs. (Notice that no apostrophe is involved in the formation of these plurals.